﻿using NPOI.HSSF.UserModel;
using NPOI.SS.UserModel;
using NPOI.XSSF.UserModel;
using System;
using System.Collections.Generic;
using System.Data;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;

public class ExcelHelper : IDisposable
{
	private string fileName = null; //文件名  
	private IWorkbook workbook = null;
	private FileStream fs = null;
	private bool disposed;
	public ExcelHelper(string fileName)//构造函数，读入文件名  
	{
		this.fileName = fileName;
		disposed = false;
	}
	/// 将excel中的数据导入到DataTable中  
	/// <param name="sheetName">excel工作薄sheet的名称</param>  
	/// <param name="isFirstRowColumn">第一行是否是DataTable的列名</param>  
	/// <returns>返回的DataTable</returns>  
	public DataTable ExcelToDataTable(string sheetName, bool isFirstRowColumn)
	{
		ISheet sheet = null;
		DataTable data = new DataTable();
		int startRow = 0;
		try
		{
			fs = new FileStream(fileName, FileMode.Open, FileAccess.Read);
			workbook = WorkbookFactory.Create(fs);
			if (sheetName != null)
			{
				sheet = workbook.GetSheet(sheetName);
				//如果没有找到指定的sheetName对应的sheet，则尝试获取第一个sheet  
				if (sheet == null)
				{
					sheet = workbook.GetSheetAt(0);
				}
			}
			else
			{
				sheet = workbook.GetSheetAt(0);
			}
			if (sheet != null)
			{
				IRow firstRow = sheet.GetRow(0);
				int cellCount = firstRow.LastCellNum; //一行最后一个cell的编号，即总的列数  
				if (isFirstRowColumn)
				{
					for (int i = firstRow.FirstCellNum; i < cellCount; ++i)
					{
						ICell cell = firstRow.GetCell(i);
						if (cell != null)
						{
							string cellValue = cell.StringCellValue;
							if (cellValue != null)
							{
								DataColumn column = new DataColumn(cellValue);
								data.Columns.Add(column);
							}
						}
					}
					startRow = sheet.FirstRowNum + 1;//得到项标题后  
				}
				else
				{
					startRow = sheet.FirstRowNum;
				}
				//最后一列的标号  
				int rowCount = sheet.LastRowNum;
				for (int i = startRow; i <= rowCount; ++i)
				{
					IRow row = sheet.GetRow(i);
					if (row == null) continue; //没有数据的行默认是null　　　　　　　  

					DataRow dataRow = data.NewRow();
					for (int j = row.FirstCellNum; j < cellCount; ++j)
					{
						if (row.GetCell(j) != null) //同理，没有数据的单元格都默认是null  
							dataRow[j] = row.GetCell(j).ToString();
					}
					data.Rows.Add(dataRow);
				}
			}
			return data;
		}
		catch (Exception ex)//打印错误信息  
		{
			MessageBox.Show("Exception: " + ex.Message);
			return null;
		}
	}

	//将DataTable数据导入到excel中  
	//<param name="data">要导入的数据</param>  
	//<param name="sheetName">要导入的excel的sheet的名称</param>  
	//<param name="isColumnWritten">DataTable的列名是否要导入</param>  
	//<returns>导入数据行数(包含列名那一行)</returns>  
	public int DataTableToExcel(DataTable data, string sheetName, bool isColumnWritten)
	{
		int i = 0;
		int j = 0;
		int count = 0;
		ISheet sheet = null;

		fs = new FileStream(fileName, FileMode.OpenOrCreate, FileAccess.ReadWrite);
		if (fileName.IndexOf(".xlsx") > 0) // 2007版本  
			workbook = new XSSFWorkbook();
		else if (fileName.IndexOf(".xls") > 0) // 2003版本  
			workbook = new HSSFWorkbook();

		try
		{
			if (workbook != null)
			{
				sheet = workbook.CreateSheet(sheetName);
			}
			else
			{
				return -1;
			}

			if (isColumnWritten == true) //写入DataTable的列名  
			{
				IRow row = sheet.CreateRow(0);
				for (j = 0; j < data.Columns.Count; ++j)
				{
					row.CreateCell(j).SetCellValue(data.Columns[j].ColumnName);
				}
				count = 1;
			}
			else
			{
				count = 0;
			}

			for (i = 0; i < data.Rows.Count; ++i)
			{
				IRow row = sheet.CreateRow(count);
				for (j = 0; j < data.Columns.Count; ++j)
				{
					row.CreateCell(j).SetCellValue(data.Rows[i][j].ToString());
				}
				++count;
			}
			workbook.Write(fs); //写入到excel  
			return count;
		}
		catch (Exception ex)
		{
			Console.WriteLine("Exception: " + ex.Message);
			return -1;
		}
	}

	public void Dispose()//IDisposable为垃圾回收相关的东西，用来显式释放非托管资源,这部分目前还不是非常了解  
	{
		Dispose(true);
		GC.SuppressFinalize(this);
	}
	protected virtual void Dispose(bool disposing)
	{
		if (!this.disposed)
		{
			if (disposing)
			{
				if (fs != null)
					fs.Close();
			}
			fs = null;
			disposed = true;
		}
	}
}

